Lead-free free-cutting silicon brass alloy

ABSTRACT

The present invention supplies a lead-free free-cutting silicon brass alloy with high zinc which preferably comprises 35.0 to 42.0 wt % Zn, 0.1 to 1.5 wt % Si, 0.03 to 0.3 wt % Al, 0.01 to 0.36 wt % P, 0.01 to 0.1 wt % Ti, 0.001 to 0.05 wt % rare earth metals selected from the group consisting of La and Ce, 0.05 to 0.5 wt % Sn, and/or 0.05 to 0.2 wt % Ni, and the balance being Cu and unavoidable impurities. The invented alloy is excellent in castability, weldability, cuttability, electroplating properties, corrosion resistance, mechanical properties. The alloy is especially applicable in castings which need cutting and welding under low pressure die casting, such as castings for faucet bodies in the water supply system. The alloy is also suitable for use in components which are produced from casting ingots by die forging.

CROSS REFERENCE TO RELATED APPLICATIONS

Not applicable.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention generally relates to a lead-free free-cuttingsilicon brass alloy, in particular a lead-free free-cutting siliconbrass alloy with high zinc which is applicable in low pressure diecastings and forgings.

BACKGROUND OF THE INVENTION

Currently, several series of casting brass alloys are in widespread use,for example, the Cu—Zn series, Cu—Zn—Si series, Cu—Zn—Al series. Eachseries includes lead-containing alloys. Lead-containing casting brassalloys have excellent cuttability, castability and low cost. However,these alloys harm the environment and the human body in the process oftheir production and usage. Furthermore, lead-containing brass alloyshave poor weldability.

The harmfulness of lead to the environment and the human body is ofgreat concern. Over the past 15 years, many patents for lead-free or lowlead free-cutting brass alloys have been published or granted in the US,China, Japan, Germany and Korea. There are twenty bismuth brass alloys(CN2005100504254, CN2003101091620, CN021219915, CN941926133,CN931200644, CN2007100674803, CN2005800014925, CN2008100659066, U.S.Pat. No. 6,599,378, U.S. Pat. No. 5,653,827, U.S. Pat. No. 5,288,458,U.S. Pat. No. 5,409,552, U.S. Pat. No. 5,630,984, U.S. Pat. No.5,614,038, US 2004/0159375, JP2000239765, JP2002003967, JP2001059123,JP2006322059, JP2003119527), ten silicon brass alloys (CN2004100891500,CN2004100042937, CN2005800194114, CN2005800464607, US20070169854, US20020069942, US 20070062615, US 20050247381, JP2000336441,JP2001064742), seven tin brass alloys (CN2004100042922, CN031551777,CN2006100056892, US 2004241038, US20040159375, JP2000087158,JP2003147460, two antimony brass alloys (CN2007100708034,CN2004100158365), one magnesium brass alloy (CN2007100359122), onealuminum brass alloy (U.S. Pat. No. 3,773,504) and one tellurium brassalloy (CN2004100222446) disclosed in the prior art. These referencesprimarily disclose lead-free free-cutting deformation brass alloys. Few,if any, references disclose lead-free alloys that are applicable incastings and/or low pressure die casting.

Published lead-free or low lead free-cutting casting bismuth brassalloys include UNS C89550 (high zinc, lead-free), UNS C89837 (low zinc,high copper, lead-free), UNS C89510 and UNS C89520 (low zinc, highcopper, lead-free), and FR CuZn39BilAl. These alloys contain smallamount of Sn and Se. The bismuth brass alloys disclosed by somereferences add expensive Se and Sn and even more expensive Te and In tochange the dispersion of Bi in the grain boundary from continuous filmto discontinuous particle. This has the beneficial effect of decreasingthe hot and cold brittleness of the bismuth brass alloy.

One disadvantage of prior art bismuth-brass alloys is that the metalsBi, Sn, Ni, Se, Te and In are relatively expensive. Another disadvantageof prior art bismuth brass alloys is that they have poor castability andweldability. Accordingly, castings made of bismuth brass alloys by lowpressure die casting are prone to cracking, resulting in a low overallyield. Also, castings made of bismuth brass alloys by brazing are alsoprone to cracking in weld and heat-affected zones. Furthermore, theforging temperature range is narrow. These are some of the obstaclespresented by bismuth brass alloys. There is a need for mass-producedfaucet bodies and valve bodies made from lead-free free-cutting brass,by low pressure die casting and weld-forming and by forging andweld-forming, respectively. Since bismuth is relatively rare andexpensive, and requires improvements in technological properties such ascastability and weldability beyond what is currently known in the art,the application and development potential of bismuth brass alloy islimited.

Current casting silicon brass alloys usually contain Pb. These alloysare highly prone to be hot cracked in the process of low pressure diecasting. Furthermore, the Pb release will exceed the requirement ofNSF61 standard.

Nowadays, research and development of lead-free or low lead free-cuttingsilicon brass alloys is typically based on brass alloys with low zincand high copper. These alloys rely on increasing the relative ratio ofhard and brittle γ phase in the alloy to ensure the free-cuttability ofthe alloy. This approach sacrifices the plasticity of the alloy and isdetrimental to casting formings and process formings. Furthermore, asthe content of Cu is high, the cost of materials is high. At present,many prior art silicon brass alloys are deformation alloys. The contentof zinc and copper in these alloys overlap, and most are silicon brassalloys with high copper. Typically, there is little discussion ordisclosure of the castability of the alloys, or their suitability forlow pressure die casting.

For example, two antimony brass alloys prior arts (CN2007100708034 andCN2004100158365) issued to Zhang et al. both disclosed Sb as one of themain elements of the alloys. But Zhang et al. do not discuss or disclosethe castability of the alloy, particularly the castability applied onlow pressure die casting. Furthermore, the Sb release of these alloysinto the water may exceed the NSF/ANSI61-2007 standard and should not beused for drinking water supply system applications.

The internal construction of faucet bodies is very complex. The faucetbodies typically are hollow castings with slim walls whose thickness canvary. The cooling intensity of the mold for low pressure die casting islarge. The alloy must have excellent castability, especially excellentmold filling performance and hot crack resistance. These kinds ofcastings also are subjected to cutting processes including, for example,sawing, lathing, milling, drilling and polishing. All these processesrequire the alloy to have excellent cuttability. There is a need formass-produced faucets made by casting and weld molding, and for valvesmade by forging and weld molding. These applications require the alloysto have excellent weldability. Additionally, standards for drinkingwater, such as NSF/ANSI61-2007 strictly restrict the amount of elementssuch as Sb, Pb, Cd, and As that can be released into the water. Forexample, under the NSF/ANSI61-2007 standard, the maximum acceptablerelease amount of Sb and Pb is 0.6 ug/L and 1.5 ug/L, respectively. Ifthe Sb content in the brass alloy exceeds 0.2 wt %, the amount of Sbrelease into the water will exceed 0.6 ug/L. Thus, some antimony brassalloys are not suitable for use in drinking water system installations.

DETAILED DESCRIPTION

One object of the present invention is to provide a free-cutting siliconbrass alloy with high zinc which is excellent in castability, forgingperformance, cuttability, weldability, mechanical properties, corrosionresistance and electroplatability and whose cost is rather lower,especially a free-cutting and weldable silicon brass alloy with highzinc which is applicable in low pressure die casting and forging. Thisalloy will solve the limitations of conventional brass alloys discussedabove especially the problem of lead contamination.

The object of the present invention is achieved by the novel selectionand composition of elements comprising the alloy.

The basic theory behind the composition of the present alloys is to usethe mutual interaction of multiple alloy elements in low amounts to formdifferent multi-element intermetallic compound grains, which improve thecuttability of the alloys and ensure excellent castability, weldability,cuttability and corrosion resistance.

The present invention comprises: 35.0 to 42.0 wt % Zn, 0.1 to 1.5 wt %Si, 0.03 to 0.3 wt % Al, 0.01 to 0.36 wt % P, 0.01 to 0.1 wt % Ti, 0.001to 0.05 wt % rare earth metals, 0.05 to 0.5 wt % Sn and/or 0.05 to 0.2wt % Ni and the balance being Cu and unavoidable impurities. Theelongation rate of the casting alloy is more than 10%. The hardness isin the range of HRB (Rockwell hardness scale B) 55 to 75. The foldingangle of the strip samples is larger than 55°.

In the present alloys, Si is a main element along with Zn. The alloysalso contain Al, Mg, Sn and P. The effects of using Si include, forexample, deoxidization for improving castability, weldability, corrosionresistance, particularly improving dezincification corrosion resistance,increasing relative ratio of β phase and forming small amount of γ phaseand improving cuttability of the alloys. The present inventiondemonstrates that Si has the effect of refining α phase grain, which isbeneficial for improving the intensity, elongation rate and crackingresistance of the alloys. Grain refining is beneficial for mechanicalproperties and cuttability because the intermetallic compounds arefurther dispersed in the grain boundary, phase boundary and graininterior. For castings with relatively complex constructions and thickcross-sections, applicable in low pressure die casting. When the contentof Si is within the maximum, no hard and brittle γ phase appears and thealloy is in β phase zone at high temperature and in (α+β′) phrase zoneat temperature lower 450° C. β phase is the intermetallic compound withdisordered body-centered crystal structure. The plasticity of β phase athigh temperatures is better than a phase, so it is beneficial for hotcracking resistance of the alloy. β′ phase is the intermetallic compoundwith ordered, body-centered crystal structure. β′ phase is harder andmore brittle than β phase so it is beneficial for cuttability. However,when the alloy is in β′ phase zone at room temperature, the brittlenessof the alloy will increase such that it is prone to cold cracking, andthe hardness will be greater than HRB 80. This is bad for cuttability.

The total zinc equivalents of Zn, Al and Si must be lower than 45 wt %.For example, if the content of Zn in the alloy is 40 wt %, Al is 0.2 wt%, the content of Si typically can't exceed 0.4 wt %. As the radial heatdissipation of the continuous casting ingots for die forging is uniform,and the axial solidification is in order, the alloy is not prone to behot cracked. Therefore, the content of Si is preferably in the range of0.6 to 1.5 wt %. For products whose construction by low pressure diecasting is relatively simple, the content of Si is preferably in therange of 0.4 to 1.3 wt % so that small amount of γ phase will be formedin the alloy for improving the cuttability.

The effects of adding Al include solid solution strengthening, corrosionresistance improvement, hot cracking resistance improvement anddeoxidization. The content of Al is preferably in the range of 0.03 to0.3 wt %. If the content of Al is lower than 0.03 wt %, its beneficialeffects are not apparent. If the content of Al is higher than 0.3 wt %,Al is prone to oxidizing and slag formation such that the fluidity ofthe alloy will be decreased. Castability and weldability are accordinglydecreased. Moreover, Al will make the silicon brass alloy grain coarserand decrease the condensability of the castings and ingots.

P is included in the inventive alloy. The solid solubility of Pin thematrix of copper will be reduced rapidly with the temperaturedecreasing. The solid solubility will be equivalent to zero when thetemperature is equivalent to the room temperature, precipitated P withCu will form brittle intermetallic compound Cu₃P. In the cuttingprocess, this intermetallic compound is prone to cracking so that thecutting chips are prone to breaking, which ensures the alloy excellentcuttability. Prior art brass alloys may add 0.003 to 0.006 wt % P fordeoxidization. When the content of P exceeds 0.05 wt %, theintermetallic compound Cu₃P will be formed. In the present alloys, thecontent of P is in the range of 0.01 to 0.4 wt %. This range of Pimproves deoxidization, which improves the castability and weldabilityof the alloy and decreases the oxidization loss of other usefulelements. And the formed Cu₃P further improves the cuttability of thealloys. Thus, in the present invention, P is beneficial for cuttability,castability and weldability. Relatively small amounts of P also have theeffect of grain refining.

The effect of Mg in the brass alloy is similar to the effect of P, thatis, deoxidization and grain refining. The intermetallic compound Cu₂Mgwhich is formed by Mg and Cu is also beneficial for improving thecuttability of the alloy. However, Cu₂Mg is not hard and brittle likeCu₃P but it is somewhat bad for the plasticity of the alloys. Mg alsowill form Mg₂Si with Si. It's found by SEM (scanning electronmicroscope) observation that Mg—Si particles are uniformly dispersedgranularly in the interior of α phase grain, grain boundary and phaseboundary. Mg—Si particles are not found in the interior of β phasegrain. Mg together with elements Sb, Cu and Zn also forms a complexintermetallic compound which is granularly dispersed in the interior ofgrains. These multi-element intermetallic compound particles are notonly beneficial for improving the cuttability of the alloys, but alsobeneficial for decreasing the loss of Mg during casting. The content ofMg will be in the range of 0.05 to 0.4 wt %, if any in the inventivealloys. This amount of Mg is sufficient for deoxidization, grainrefining and improving the castability of the alloys. If the content ofMg is in the middle to upper limits of the specified range, it is alsobeneficial for the cuttability. Mg is better than P at improving thecastability of the alloys. Mg improves the hot cracking resistance ofthe alloy and effectively eliminates the cracking of the castings.

Rare earth metals are a group of elements consisting of La and Ce. Tiand rare earth metals are effective grain refiners and also have theeffect of deoxidization. Rare earth metals also have the effect ofpurifying the grain boundary. Rare earth metals will form high meltingpoint intermetallic compounds with low melting point impurities in thegrain boundary and therefore decrease the hot brittleness of the alloysor form intermetallic compounds with other harmful impurities in thegrain boundary and therefore decrease the harmfulness of harmfulimpurities. Rare earth metals also could mutually interact with mostalloying elements and form more stable intermetallic compounds.Therefore, rare earth metals and Ti are typically added to lead-freefree-cutting brass alloys. However, rare earth metals are prone tooxidizing. Even if only a small quantity is added, the flowability ofthe alloys will decrease. The inventive alloys selectively add 0.001 to0.05 wt % rare earth metals. This amount of rare earth metals willimprove the mechanical performance, but is bad for the castability, asembodied in volume shrinkage samples wherein the face of theconcentrating shrinkage cavity is not smooth and small visible shrinkageporosity in the bottom of the concentrating shrinkage appears.

The selective addition of Ni is for solid solution strengthening,corrosion resistance improvement and especially the stress corrosionresistance improvement of the alloys. However, when Al is also added tothe alloys, Ni together with Al will form hard and brittle intermetalliccompounds with high melting points. This will decrease the alloy'splasticity. The selective addition of Sn improves the corrosionresistance of the alloys, especially the dezincification corrosionresistance of the alloys. Sn also can form intermetallic compounds withSb. With increased addition of Sn, Sb release amount into the water willdecrease. When the content of Sb exceeds 0.2 wt %, however, even if thecontent of Sn increases, the Sb release amount into the water willexceed the NSF/ANSI61-2007 standard as well as result in graincoarsening. The cracking resistance, intensity and elongation rate willdecrease. The effect that Sn decreases Sb release amount into the wateris very limited. Since Ni and Sn are very expensive, their levels arebetter kept around lower limit.

Fe is a common impurity in copper and copper alloys. It has the effectof refining α phase grain in copper and brass. The solid solution of Feat room temperature is very low. Fe without solid solution or Feprecipitated from solid solution will decrease the plasticity andcorrosion resistance of the alloys and form hard and brittle hard spotswith Al, Si and B. The hard spots may be located in the face of castingsand forgings and then influence the facial quality of the electroplatedproducts. The facial glossiness of products is affected by these spotdiscrepancies. Therefore, the content of Fe should be equal or lowerthan 0.1 wt %.

The content of Pb should be equal or lower than 0.1 wt %. This level isbeneficial for cuttability improvement and the release amount into thewater will not exceed the standard NSF/ANSI61-2007. (1.5 ug/L)

Sb as an unavoidable impurity should be equal or lower than 0.04 wt %.At this level, the Sb release amount into the water will not exceed thestandard NSF/ANSI61-2007(0.6 ug/L).

For obtaining both castability and cuttability of the alloys, the alloycomposition should meet the following requirements: the elongation rateof As-Cast alloy should be larger than 5%, the hardness is in the rangeof HRB 55 to 75, and the bending angle of strip samples is preferablylarger than 55°.

The advantages of the invented alloy include, but are not limited to:excellent castability and weldability, satisfactory performance inprocesses such as casting, forging, welding, sawing, lathing, milling,drilling, polishing and electroplating, and desirable properties forfaucet bodies including stress corrosion and salt spray corrosionresistance, dezincification corrosion resistance, low Pb releaseamounts, low Sb release amounts, low water leakage, and improvedmechanical performance and hardness. The inventive alloys have excellentforging performance and the range of forging temperature is large.Ingots rather than extruded bars could be disposably die forged tocomponents with complex structure. This is beneficial for recycling andre-use of Pb brass alloy, phosphorus brass alloys, magnesium brassalloys, antimony brass alloys, silicon brass alloys and common brassalloys. Furthermore, metal materials cost and total production costs arelower.

The steps of manufacturing of the invented alloy are as follows:Material proportioning—melting in the intermediate frequency inductionelectric furnace (with flux for refining)—pouring to beingots—remelting—low pressure die casting to be castings or horizontalcontinuous casting to be rod—flaying—forging. The temperature for lowpressure die casting is in the range of 970° C. to 1000° C. Thetemperature for horizontal continuous casting is in the range of 990° C.to 1030° C. The temperature for forging is in the range of 600° C. to720° C.

The advantages of the present manufacturing method include strongoperability. In other words, the present universal production equipmentsand tool and die and even low pressure die casting mold and sand corefor brass continuous casting, low pressure die casting and forging maybe used without a redesign or revision.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 shows the characteristics of volume contraction samples formed inExample 1 of Table 1.

FIG. 2 shows the characteristics of volume contraction samples formed inExample 14 of Table 1.

FIG. 3 shows the shapes of the cutting chips formed in Example 1 ofTable 1.

FIG. 4 shows the shapes of the cutting chips formed in Example 6 ofTable 1.

FIG. 5 shows the shapes of the cutting chips formed in Example 14 ofTable 1.

FIG. 6 shows the shapes of the cutting chips formed in cuttinglead-contained brass alloy C36000 for comparison.

EXAMPLES

Examples of alloys according to the present invention are shown inTable 1. The raw materials used in the alloys include: No. 1 Cu, No. 1Zn, A00 Al, No. 1 Ni, No. 1 Sn, Cu—Si master alloy, Cu—P master alloy,Cu—Ti master alloy, misch metal, magnesium alloys, old materials of No.1 Pb ingots or C36000, the covering agent, and flux as the refiningagent.

One method of manufacturing the alloys is as follows. First, No. 1 Cu,Cu—Si master alloys, No. 1 Ni, and the covering agent that enhances slagremoval efficiency are added to the furnace. These materials are heateduntil they have melted to form a melt mixture and are thereafterstirred. Then the No. 1 Zn is added to the melt mixture, melt and bestirred. Slag is skimmed from the melt and is covered. Then flame throwis processed. Thereafter, Cu—P master alloys and Magnesium alloys areadded and the mixture is stirred. The left metal materials are added.These materials are again heated until melted, and are thereafterstirred. The flux for refining is added and the mixture stands until theingots are formed. Then the low pressure die casting occurs at thetemperature in the range of 970 to 1000° C. or horizontal continuouscasting occurs at the temperature in the range of 990° C. to 1030° C.after the ingots are remelted. Finally, the hot forging is processed atthe temperature in the range of 600 to 720° C.

TABLE 1 Composition of example alloys (wt %) rare Example Cu Si Al P SnNi Mg Ti earth Pb + Fe Zn 1 59.79 0.34 0.20 0.10 0.09  0.104 — — 0.003<0.3 Balance 2 60.15 0.34 0.18 0.16 0.09  0.106 0.25 — — <0.3 Balance 360.20 0.38 0.24 0.12 0.15 0.11 — — 0.004 <0.3 Balance 4 59.83 0.36 0.260.15 0.08 — 0.10 — 0.001 <0.3 Balance 5 59.61 0.39 0.27 0.14 0.14 — —0.05 — <0.3 Balance 6 61.11 0.12 0.06 0.28 0.12 0.11 0.12 — 0.002 <0.3Balance 7 59.86 0.14 0.23 0.31 0.15 — — — 0.005 <0.3 Balance 8 59.340.15 0.25 0.29 0.18 — —  0.013 — <0.3 Balance 9 60.20 0.12 0.09 0.27 — —0.10 — — <0.3 Balance 10 60.37 0.15 0.31 0.31 — 0.13 — 0.03 — <0.3Balance 11 60.55 0.20 0.34 0.36 — — 0.13 — 0.002 <0.3 Balance 12 61.040.18 0.25 0.06 — — 0.28 — — <0.3 Balance 13 60.69 0.21 0.28 0.05 0.11 —0.30 — — <0.3 Balance 14 60.31 0.25 0.24 0.08 0.09 0.14 0.35 — — <0.3Balance

Examples 1, 6 and 14 were used to make 3 different types of faucetbodies by low pressure die casting and weld-forming. The formability wasacceptable.

The temperature for low pressure die casting of the example alloy is inthe range of 970 to 1000° C. The pouring temperature for testingcastability is 1000° C. The lead-free brass alloy of present inventionhas been tested with results as follows:

Castability Test

Four kinds of standard casting alloy samples were used to measure thecastability of the alloy. The volume shrinkage samples are forevaluating the characteristics of concentrating shrinkage, dispersedshrinkage and porosity. Spiral samples are for measuring the flow lengthof the alloy melt. Strip samples are for measuring linear shrinkage rateand bend angle of the alloy. The cylindrical samples with different wallthickness are for measuring shrinkage crack resistance of the alloy. Forvolume shrinkage samples, as may be seen in Table 2, if the face of theconcentrating shrinkage cavity is smooth, there is no visible shrinkageporosity in the bottom of the concentrating shrinkage cavity, and thereis no visible dispersed shrinkage cavity in the section of the samples,then this indicates castability is excellent and is shown as “o” inTable 2.

If the face of the concentrating shrinkage cavity is smooth but theheight of visible shrinkage porosity in the bottom of the concentratingshrinkage cavity is less than 5 mm, and there is no visible dispersedshrinkage cavity in the section of the samples, this indicatescastability is good, and is shown as “□” in Table 2.

If the face of the concentrating shrinkage cavity is not smooth and theheight of visible shrinkage porosity in the bottom of the concentratingshrinkage cavity is more than 5 mm, whether or not there is dispersedshrinkage cavity in the section of the samples, this indicatescastability is poor, and is shown as “x” in Table 2.

For cylindrical samples, as may be seen in Table 2, if no visible crackis shown on the casting or polished surface, this indicates castabilityis excellent and will be shown as “o” in Table 2. If the visible crackis shown, this indicates the castability is poor, and will be shown as“x” in Table 2.

TABLE 2 Castability of the invented alloy examples Examples 1 2 3 4 5 67 8 9 10 11 12 13 14 C36000 Concentrating ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Δ ∘shrinkage Flowing 410~470 410~460 400~430 400 Length/mm Linear shrinkage1.4~1.7 2.1 rate/% Bend angles/° >90 50 75 75 60 80 70 60~65 50~55 Wall2.0 mm ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ x ∘ ∘ x ∘ sickness 3.5 mm ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘∘ ∘ ∘ ∘ ∘ 4.0 mm ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ HRB  60 76 70 63~70 6962~71 65~73 44

Cuttability:

Many measures can be used to evaluate cuttability. One way is todetermine the relative cutting ratio of the invented alloy by measuringthe cutting resistance and assuming the relative cutting ratio of thelead-contained brass alloy such as C36000 is 100%. The relative cuttingratio of the present example is shown as follows:

${{Relative}\mspace{14mu} {cutting}\mspace{14mu} {ratio}} = {\frac{{Cutting}\mspace{14mu} {resistance}\mspace{14mu} {of}\mspace{14mu} {alloy}\mspace{14mu} {C36000}}{{Cutting}\mspace{14mu} {resistance}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {invented}\mspace{14mu} {alloy}} \times 100\%}$

The samples for testing cuttability are selected from the sprue portionsof the castings made for tensile testing. The feeding quantity is 0.5mm. Other cutting parameters are the same. The results are shown inTable 3.

Mechanical Properties

The mechanical properties test results are shown in Table 3.

TABLE 3 Mechanical properties and relative cutting ratio of the inventedalloy examples Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 14 C36000 RemarkTensile Manual 400 — 450 460 370 420 410 — 430 340 Tensile samples bystrength/ Casting manual casting and MPa Horizontal 430 450 — — 410 — —440 — — low pressure die continuous casting is without castingmachining; Tensile Low 465 — — — 385 — — — — — samples for pressurehorizontal die casting continuous casting Elongation Manual 13 —  9  1012  8  6 —  8 — are φ10 mm rate/% Casting samples machined Horizontal 26 15 — — 40 — —  13 — — from φ40 mm continuous casting bars. casting Low8.5 — — — 9 — — — —  37 pressure die casting Relative cutting ≧80 — ≧80— — ≧85 — 100 ratio/%

Corrosion Resistance:

The samples for testing corrosion resistance are As-Cast. The samples ofExamples 1, 6 and 14 are from faucet bodies formed by low pressure diecasting. The samples of other Examples are ring samples which aretypically for measuring the castability, as they cannot free shrink inthe process of solidification and cooling and their internal stress isrelatively large. The samples for testing salt spray corrosion andstress corrosion resistance are electroplating products. The stresscorrosion resistance test was conducted according to GSO481.1.013-2005standard (Ammonia fumigation). The salt spray corrosion resistance testwas conducted according to ASTMB368-97(R2003)E1 standard. Thedezinfication corrosion resistance test was conducted according toGB10119-1988 standard. The test of metal release amount was conductedaccording to NSF/ANSI61-2007 standard. The test results are shown inTable 4.

TABLE 4 Corrosion results of the invented alloy examples Averagedezincification Stress Salt spray layer depth/mm Metal release corrosioncorrosion Alloy amount Q Examples resistance resistance Castings ingotsValue/μg/L 1 Eligible Eligible 0.24 0.26 Sb < 0.6 2 Eligible Eligible0.28 Pb < 1.5 3 Eligible Eligible 0.23~0.27 As < 1.0 4 Eligible EligibleCd < 0.5 5 Eligible Eligible Hg < 0.2 6 Eligible Eligible 0.25 0.28Eligible 7 Eligible Eligible 0.24~0.31 8 Eligible Eligible 9 EligibleEligible 0.26~0.33 10  Eligible Eligible 11  Eligible Eligible 12 Eligible Eligible 0.26 0.31~0.38 13  Eligible Eligible 14  EligibleEligible C36000 Eligible Eligible 0.40 Pb > 0.5, Other eligible

1. A lead-free free-cutting silicon brass alloy comprising: 35.0 to 42.0wt % Zn, 0.1 to 1.5 wt % Si, 0.03 to 0.3 wt % Al, 0.01 to 0.36 wt % P,0.01 to 0.1 wt % Ti, 0.001 to 0.05 wt % rare earth metals selected fromthe group consisting of La and Ce, 0.05 to 0.5 wt % Sn, optionally 0.05to 0.2 wt % Ni, and the balance being Cu and unavoidable impurities,wherein an elongation rate of casting of the alloy is greater than 10%,hardness of the alloy is in a range of HRB 55 to 75, and a bending angleof strip samples of the alloy is more than 55°.
 2. The lead-freefree-cutting silicon brass alloy of claim 1 comprising 39.00 to 42.00 wt% Zn, and 0.1 to 0.3 wt % P.
 3. The lead-free free-cutting silicon brassalloy of claim 1, comprising 39.00 to 42.00 wt % Zn, 0.1 to 0.2 wt % Si,0.15 to 0.3 wt % P, 0.05 to 0.1 wt % Sn, 0.05 to 0.1 wt % Ni and 0.05 to0.1 wt % Ti.
 4. The lead-free free-cutting silicon brass alloy of claim1, comprising 39.00 to 42.00 wt % Zn, 0.1 to 0.5 wt % Si, 0.15 to 0.25wt % P, 0.05 to 0.2 wt % Sn, and 0.001 to 0.01 wt % rare earth metalsselected from the group consisting of La and Ce, and further comprising0.05 to 0.4 wt% Mg.
 5. The lead-free free-cutting silicon brass alloywith high zinc of claim 1, comprising 40.00 to 42.00 wt % Zn, 0.1 to 0.2wt % Si, 0.05 to 0.3 wt % Mg, 0.01 to 0.3 wt % P, 0.1 to 0.3 wt % Sn and0.05 to 0.1 wt % Ni and further comprising 0.05 to 0.3 wt% Mg.
 6. Thelead-free free-cutting silicon brass alloy of claim 1 comprising 40.00to 42.00 wt % Zn, 0.2 to 0.5 wt % Si, 0.01 to 0.1 wt % P, 0.1 to 0.3 wt% Sn, 0.05 to 0.15 wt % Ni, and 0.001 to 0.04 wt % rare earth metalsselected from the group consisting of La and Ce, and further comprising0.1 to 0.25 wt% Mg.
 7. A lead-free free-cutting silicon brass alloycomprising: 35.0 to 42.0 wt % Zn, 0.1 to 1.5 wt % Si, 0.03 to 0.3 wt %Al, 0.01 to 0.36 wt % P, 0.01 to 0.1 wt % Ti, 0.001 to 0.05 wt % rareearth metals selected from the group consisting of La and Ce, 0.05 to0.5 wt % Sn, optionally 0.05 to 0.2 wt % Ni, and the balance being Cuand unavoidable impurities.
 8. The lead-free free-cutting silicon brassalloy of claim 7 comprising 39.00 to 42.00 wt % Zn, and 0.1 to 0.3 wt %P.
 9. The lead-free free-cutting silicon brass alloy of claim 7,comprising 39.00 to 42.00 wt % Zn, 0.1 to 0.2 wt % Si, 0.15 to 0.3 wt %P, 0.05 to 0.1 wt % Sn, 0.05 to 0.1 wt % Ni and 0.05 to 0.1 wt % Ti. 10.The lead-free free-cutting silicon brass alloy of claim 7, comprising39.00 to 42.00 wt % Zn, 0.1 to 0.5 wt % Si, 0.15 to 0.25 wt % P, 0.05 to0.2 wt % Sn, and 0.001 to 0.01 wt % rare earth metals selected from thegroup consisting of La and Ce, and further comprising 0.05 to 0.4 wt%Mg.
 11. The lead-free free-cutting silicon brass alloy of claim 7,comprising 40.00 to 42.00 wt % Zn, 0.1 to 0.2 wt % Si, 0.01 to 0.3 wt %P, 0.1 to 0.3 wt % Sn and 0.05 to 0.1 wt % Ni, and further comprising0.05 to 0.3 wt% Mg.
 12. The lead-free free-cutting silicon brass alloyof claim 7 comprising 40.00 to 42.00 wt % Zn, 0.2 to 0.5 wt % Si, 0.01to 0.1 wt % P, 0.1 to 0.3 wt % Sn, 0.05 to 0.15 wt % Ni, and 0.001 to0.04 wt % rare earth metals selected from the group consisting of La andCe, and further comprising 0.1 to 0.25 wt% Mg..